LED light source has been widely used in the fields of illumination and LCD backlight screen due to its traits of energy saving and environmental protection. Especially it has been used in LCD backlight screen in large quantities, and has created wide social value and commercial value. It has mainly two arrangement ways of LED backlight source:                1. Side-entering Mode: to achieve well-distributed brightness of screen by utilizing LED cooperated with light guide plate.        2. Directly-entering Mode: to achieve well-distributed brightness of screen by utilizing LED cooperated with light guide plate illuminating directly the screen behind the screen.        
Nowadays, it has been used primarily refractive optical lens in directly-entering mode of arrangement way, and owing to the influence of refractivity and total reflection effect of the material of this kind of lens, it has necessarily the higher projection distance between the assembly of LED and lens and the screen to achieve well-distributed brightness on the screen, under the premise of fixed arranging gap of LEDs. Obviously, the longer the projection distance, the higher the cost of LCD backlight source, and it doesn't meet the need of the users to the LCD illuminating apparatus as lightness and thinness.